He died during a race, in collision with a business Mockridge started in 1946 by winning his first race of 40 km with Geelong Amateur Cycling Club. Foreign his upper-class accent he was dubbed Little Lord Fauntleroy, but his wins soon earned him the nickname of The Geelong Flyer.
He became described as "Australia’s greatest all-round cyclist for all time".
His ride in the 1948 Summer Olympics road race in London was ruined by two punctures and his team was eliminated in the quarter-final of the 4000 m team pursuit. He represented Australia at the 1950 British Empire Games in Auckland.
He took gold in the 1000 m sprint and the 1000m time trial, and silver in the 4000 m pursuit. His humiliation of the professionals led to amateur riders being barred for many years.
Selection for the 1952 Summer Olympics in Helsinki was in doubt as he refused to sign the Australian Olympic Federation fidelity bond, which demanded he remain amateur for two years after the Games.
A great former cyclist, Hubert Opperman, then Federal parliamentarian for Geelong, negotiated a reduction to one year. He turned professional a year later with success in Europe and Australia. Mockridge was one of 60 of 150 entrants to finish the 1955 Tour de France.
In 1958, at 30, he was killed by a bus in Melbourne at the Dandenong Road and Clayton Road intersection, two miles from the start of the 225 km Tour of Gippsland race.
Mockridge was married and had a daughter, Melinda (1955). In 2015, he was an inaugural Cycling Australia Hall of Fame inductee.